1. Field of Invention
The invention relates generally to optical technologies and more particularly to an optical Wavelength Division Multiplexing (WDM) devices with multiple ports.
2. Description of Related Art
Fiber optic networks are becoming increasingly popular for data transmission due to their high speed and high data capacity capabilities. Multiple wavelengths may be transmitted along the same optical fiber. This totality of multiple combined wavelengths comprises a single composite transmitted signal. A crucial feature of a fiber optic network is the separation of the optical signal into its single wavelengths, or “channels”, typically by a dense wavelength division multiplexer. This separation must occur in order for the exchange of wavelengths between signals on “loops” within networks to occur. The exchange occurs at connector points, or points where two or more loops intersect for the purpose of exchanging wavelengths.
Add/drop systems exist at the connector points for the management of the channel exchanges. The exchanging of data signals involves the exchanging of matching wavelengths from two different loops within an optical network. In other words, each signal drops a channel to the other loop while simultaneously adding the matching channel from the other loop.
Traditional methods used by dense wavelength division multiplexers in separating an optical signal into its single channels include the use of filters and fiber gratings as separators. A “separator,” as the term is used in this specification, is an integrated collection of optical components functioning as a unit which separates one or more channels from an optical signal. Filters allow a target channel to pass through while redirecting all other channels. Fiber gratings target a channel to be reflected while all other channels pass through. Both filters and fiber gratings are well known in the optical art.
In a conventional solution, a WDM device comprises two collimators where both collimators employ the same type of grin lens for processing a light signal. While this structure may provide sufficient performance for a coarse wdm as well as 400 GHz and 200 GHz filter, as the level of the filter increases, the coupling effect between the two collimators in the WDM device will likely produce a significant amount of distortion, resulting in poor insertion loss. Accordingly, it is desirable to have a WDM device that compensates for filter distortion, thereby reducing the amount of insertion loss.